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sample-controller: add usage instructions to README

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- add usage instructions
- add Use Cases, Defining Types and Clean Up section. Copied
from apiextensions-apiserver/examples/client-go. This is done
to be consistent with all other examples.
- fix formatting

Kubernetes-commit: cdcc6ac3751ab7b04bda5bcd5fc82d236d940cc5
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Nikhita Raghunath 2017-10-22 15:05:37 +05:30 committed by Kubernetes Publisher
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README.md
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@ -3,6 +3,12 @@
This repository implements a simple controller for watching Foo resources as
defined with a CustomResourceDefinition (CRD).
This particular example demonstrates how to perform basic operations such as:
* How to register a new custom resource (custom resource type) of type `Foo` using a CustomResourceDefinition.
* How to create/get/list instances of your new resource type `Foo`.
* How to setup a controller on resource handling create/update/delete events.
It makes use of the generators in [k8s.io/code-generator](https://github.com/kubernetes/code-generator)
to generate a typed client, informers, listers and deep-copy functions. You can
do this yourself using the `./hack/update-codegen.sh` script.
@ -17,16 +23,68 @@ Changes should not be made to these files manually, and when creating your own
controller based off of this implementation you should not copy these files and
instead run the `update-codegen` script to generate your own.
# Purpose
## Purpose
This is an example of how to build a kube-like controller with a single type.
# Compatibility
## Running
```sh
# assumes you have a working kubeconfig, not required if operating in-cluster
$ go run *.go -kubeconfig=$HOME/.kube/config
# create a CustomResourceDefinition
$ kubectl create -f artifacts/examples/crd.yaml
# create a custom resource of type Foo
$ kubectl create -f artifacts/examples/example-foo.yaml
# check deployments created through the custom resource
$ kubectl get deployments
```
## Use Cases
CustomResourceDefinitions can be used to implement custom resource types for your Kubernetes cluster.
These act like most other Resources in Kubernetes, and may be `kubectl apply`'d, etc.
Some example use cases:
* Provisioning/Management of external datastores/databases (eg. CloudSQL/RDS instances)
* Higher level abstractions around Kubernetes primitives (eg. a single Resource to define an etcd cluster, backed by a Service and a ReplicationController)
## Defining types
Each instance of your custom resource has an attached Spec, which should be defined via a `struct{}` to provide data format validation.
In practice, this Spec is arbitrary key-value data that specifies the configuration/behavior of your Resource.
For example, if you were implementing a custom resource for a Database, you might provide a DatabaseSpec like the following:
``` go
type DatabaseSpec struct {
Databases []string `json:"databases"`
Users []User `json:"users"`
Version string `json:"version"`
}
type User struct {
Name string `json:"name"`
Password string `json:"password"`
}
```
## Cleanup
You can clean up the created CustomResourceDefinition with:
$ kubectl delete crd foos.samplecontroller.k8s.io
## Compatibility
HEAD of this repository will match HEAD of k8s.io/apimachinery and
k8s.io/client-go.
# Where does it come from?
## Where does it come from?
`sample-controller` is synced from
https://github.com/kubernetes/kubernetes/blob/master/staging/src/k8s.io/sample-controller.